1. Field of the Invention
The present invention provides a system for determination of the carbon concentration in fly ash and, more specifically, it permits automated determination of the amount of carbon in fly ash by interrogating the fly ash with microwave energy and determining the amount of microwave energy absorbed thereby.
2. Description of the Prior Art
The importance of determining the carbon content of fly ash, such as is produced in coal burning boilers, has long been known. For example, fly ash can be a marketable combustion product for utility companies which burn coal in order to generate electrical energy. In general, when carbon levels are greater than about 3 percent in fly ash, the fly ash becomes unsalable. Fly ash is known to be usable in the cement replacement market.
When the carbon content is too high to permit marketing of the fly ash to such users as the cement replacement market or the ready mixed concrete producers, not only is there a loss of potential sales revenue, but also there is the burden of disposal costs.
The quantity of fly ash carbon may also be viewed as a loss of potential fuel due to less than complete burning. Determination of unburned carbon by conventional methods is time consuming, and as a result, is not available to plant operators on a timely basis. If there were a way of determining carbon content promptly, adjustments could be made to the combustion process that would minimize carbon content in the fly ash, i.e., unburned fuel loss.
Among other known uses of fly ash are as fillers in plastics and asphalt, as a source of activated carbon for water and sludge treatment, as a source of magnetite for coal cleaning as well as for use in structural fills and backfill embankments, landfill covers, soil amendment and pavement base courses.
It has been known that the carbon content in fly ash can be determined by employing microwave energy which passes through a fly ash sample and measuring the unabsorbed microwave energy. In one embodiment, temperature differential in a waterwall is measured. An electronic device, sensitive to microwave power is also suggested in a general manner. See U.S. Pat. Nos. 4,663,507 and 4,705,409. See also, a paper entitled "A New Method For Improving the Salability of Fly Ash" by Trerice and DiGioia presented at the American Public Power Association Engineering and Operations Workshop in New Orleans, La. on Mar. 15-17, 1988 which shows collection and interrogation apparatus.
Despite the foregoing known systems, there remains a real and substantial need for improved means for measuring the carbon content of fly ash in an efficient and timely manner.